1. Technical Field
This invention relates to a system and method for determining the distance and direction of an acoustic emission, and more particularly to a system and method for locating fatigue points which minimizes the number of sensors needed to locate a fatigue point on a structure.
2. Discussion
Once a structural device, such as an airplane or a bridge, is put into service, it becomes necessary to detect and pinpoint fatigue points on the structure as they occur in order that they can be repaired. Because visual inspection can be both time consuming as well as inaccurate, acoustic sensors have been employed to detect fatigue points as they occur on the structure. One known application involves deploying a multitude of sensors over the surface of the structure. When a fatigue point occurs, the acoustic wave generated by the fatigue point is sensed by the acoustic sensors. Using the technique of geometric triangulation, the location of the fatigue point can be determined. One disadvantage, however, with this application is that each individual sensor has only a limited area of coverage. Therefore, a great number of individual sensors is required to cover large areas such as an aircraft skin. In this prior system, each sensor operates independently and the task of interpretating the sensor data and triangulating to determine the location of the fatigue point is processed at a central, or host, computer. Thus, a second disadvantage lies in the fact that as the size of the surface area desired to be monitored increases, the number of independent acoustic sensors increase, which results in increased complexity in both the wiring and the triangulation task of the central computer.